There are known many methods and apparatus (devices) for fluid filtration.
Most fluid filtration apparatus include filter element. Some fluid supply systems are normally constructed to have unfiltered return fluid enter the bottom of a filter element mounted in the reservoir, but some apparatus (devices) use the return fluid filter assemblies located within fluid supply reservoirs.
For instance, the reservoir, described in the U.S. Pat. No. 3,847,243, includes a return fluid compartment located below the filter assembly and return fluid plumbing is connected to the compartment which is in turn connected in fluid communication with the bottom of a filter element.
This patent has the further drawback that in the event of a failure in the return fluid plumbing or in components connected thereto, a considerable amount of fluid might drain from the reservoir due to the failure or might have to be drained from the reservoir before the failed component can be replaced.
In others of these systems, as represented by U.S. Pat. No. 3,960,174, the return fluid plumbing is connected directly in communication with the lower end of the filter element.
Such devices have a common drawback, i.e.: the unfiltered fluid in the apparatus will drain from the filter element as the latter is being withdrawn from the reservoir for replacement.
For example, the device by U.S. Pat. No. 4,343,697 includes a pair of return fluid filters supported within a main cavity of a hydraulic fluid reservoir for receiving fluid from the bottoms of respective return fluid cavities defined by a housing fixed to a top wall of the reservoir. The apparatus by this patent does not have that deficiency, because the return fluid inlet is located in the filter at a level above that to which the reservoir containing the filter assembly is intended to be filled, but this device requires a considerable amount of space in the top of the reservoir to be kept empty. The appropriate access covers close the cavities and are connected to the return fluid filters and to respective removable bottom plates of the cavities such that the filters may be withdrawn from the main cavity, via the return fluid cavities, for service or replacement. All cavities are provided with a bypass valve which acts to bypass return fluid directly from the associated return fluid cavity to the main cavity in the event that the associated filter becomes clogged. The switches, which are respectively operated in response to movement of the bypass valves to their bypass position to energize a light to indicate the clogged filter condition to an operator, are mounted on the housing in alignment with the bypass valves. The device comprises the housing which defines two separate return fluid cavities. The access to the first cavity is vertically aligned upper and lower circular openings. The top opening is closed by an access cover releasably held in place by a plurality of cap screws. The bottom opening is blocked by a circular plate, having a seal located in its periphery of the plate. Specifically, the plate is provided with a centrally located threaded hole disposed in vertical alignment with a threaded blind bore located in the lower end of a projection formed integrally with the underside of the access cover. The device also includes a plurality of bolts, a piece of hexagonal bar stock which is fixed to the lower end of one of the bolts for engagement to facilitate tightening. The mating ends of the filter elements are centered by means of a guide member. The first hole in the plate establishes fluid communication between the first cavity and the top end of the stacked filter elements while the second hole in the guide member insures free fluid flow from the upper to the lower one of the elements. The second cavity is similar to the first cavity and is vertically aligned upper and lower circular openings. An access cover is releasably fixed over the opening.
Additionally, a first return fluid conduit enters the bottom wall of the reservoir and is coupled to a return fluid inlet port located in the bottom wall of the first return fluid cavity at approximately the full level. Similarly, a second return fluid conduit enters the bottom wall of the reservoir and is coupled to a return fluid port located in the bottom wall of the second return fluid cavity. The conduits form part of the return fluid plumbing of first and second hydraulic subsystems. Fluid is supplied to the first and second sub-systems by means of first and second fluid supply conduits extending through the bottom wall of the reservoir. The housing also defines defines portions of separate bypass valve assemblies located within the first and second return fluid cavities and including appropriate vertical valve bores having bottom ends in direct fluid communication with the main cavity, at a level below the full level, and having upper ends in direct fluid communication with the first and second return fluid cavities. Upon the filter elements becoming clogged, the pressure in the first cavity will shift downwardly to a bypass position to unblock a bypass port connecting the bore in fluid communication with the main cavity and to permit the switch to open passage.
The apparatus by this patent is complex and not efficient.
The other types of the fluid (e.g., oil) are well known. The prior art has recognized the desirability of providing bypass means to permit oil to pass around the filter element when it becomes clogged. The U.S. Pat. No. 3,239,062 discloses an oil filter assembly including a single cylindrical filter element.
One of the inherited deficiencies is: the structure is not easily adapted to a wide variety of installations. The removal of the cover can lead to a loss of oil from the housing. Also, the indicator extends through the housing provides an additional sealing problem and exposes the indicator mechanism to damage.
Some types of the fluid filters can include the plurality of cylindrical filter elements. For example, the fluid filter by U.S. Pat. No. 3,819,052 comprises a first cylindrical filter housing having an open top is at least partially surrounded by a second housing forming a passageway therebetween. A baffle with a central opening is mounted in the open top and a cylindrical filter element is yieldably biased against the baffle member in the first housing. A dome-shaped cover is attached on top of the second housing to provide a flow path for fluid flowing from the passageway to the central opening in the baffle member into the filter element for passage through the filter element and then through an opening in the second housing. A combiNat. and husbandion bypass-indicator member is attached to the top of the movable filter element for guided sliding movements in the central opening of the baffle member. The described oil filter includes a first cylindrical inner filter housing with a wall including a lower portion and a reduced diameter upper portion. The upper and lower portions are joined along a plane intersecting that housing at an angle of approximately 45°. Housing has an open top end terminating in a circular edge lying in a horizontal plane. The bottom end of housing is closed off by means of a bottom end member having a drain plug secured in an opening therein. Surrounding the upper portion of first housing is a second housing (outer wall) having the same diameter as lower portion. Second housing is cylindrically shaped configuration and terminates in an upper edge, which is a circular and lies in a horizontal plane position. Second housing defines an annular passageway which is located between upper portion and second housing. Passageway is closed along plane by means of an outwardly extending flange. The annular space between upper edges is open. A fluid inlet opening is provided in outer housing directly across from an outlet opening in the first housing. A cylindrical filter elements are mounted in the filter chamber of housing between spring and baffle. The clean fluid (oil), after passing through the filter elements is discharged into the inner housing from where it passes downwardly through openings in the bottom end of the coupled member. The bottom end of inner housing is secured in an opening extending into a separate clean oil chamber. The clean oil leaves the chamber through an outlet opening.
The U.S. Pat. No. 4,783,271 discloses a filter assembly filtering the fluid and comprising two filter elements and a structure for directing the fluid first through one filter and then through the other. The filter assembly includes a mechanism for sensing the temperature of the fluid and a valve, which is responsive to the temperature-sensing mechanism. The valve is arranged in parallel with the upstream filter so that, when the fluid temperature reaches a predetermined value as sensed by the sensing mechanism, the valve opens, allowing the fluid to bypass the upstream filter and flow through the coarser downstream filter.
The apparatus disclosed by the U.S. Pat. No. 5,067,454 is related an automatic self-compensating flow control system. The device provides the fluid pulling from a reservoir by means of a suitable pump through a replaceable filter assembly which incorporates a controlled bypass valve which, together with the filter assembly is an integral part of the pump assembly.
The bypass valve allows essentially dirty oil to be supplied to the components of the drive system requiring lubrication in emergency situations during which the oil filter is clogged.
The U.S. Pat. No. 6,908,545 describes the hydraulic filter. The hydraulic fluid filter utilizes a priority valve installed in a manifold to allow for continuous filtration of hydraulic fluid up to a predetermined flow value and diverts occasional high flow to a secondary circuit. This arrangement provides a low pressure drop at a high flow condition. Particularly, this device for fluid (hydraulic fluid) filtration is related to a filter assembly for high pressure, high flow rate and low pressure drop applications. Fluid cleanliness is an important property of hydraulic fluid, as well as any fluid used in the human needs. The level of undesirable contaminants in the hydraulic fluid affects the quality of system performance, as well as the useful life of substantially all of the working hydraulic components within a hydraulic apparatus. All moving components in contact with the fluid are vulnerable to wear, and attendant premature failure if such contaminants are not removed from the apparatus. The proper cleaning of the fluid to remove undesirable contaminants can significantly lengthen the life of the apparatus' components, as well as reduce maintenance and its attendant costs. Effective cleanliness control results the reliability and performance of the system. Maintenance of a clean fluid requires efficient filtration. A number of methods have been utilized to control the cleanliness of the fluid in hydraulic apparatus. For example, a filter may be interposed in line before the load to provide full flow filtering. This method is effective in many types of systems having relatively low fluid flow. Interposing a filter in line before the load is often impractical in those high pressure systems with relatively large fluid flows. Further, maintaining filter elements in such an environment is generally quite expensive. Alternately, full flow filtering may be provided after fluid has serviced the load. In this method of filtering, a filter is typically interposed in the return line between the load and the sump. Additionally, as return line filters become dirty, they develop back pressure. The development of back pressure can be a problem in that a number of valving systems do not perform properly with the application of back pressure. An additional method of filtering disposes a filter in the sump. By nature, these filters are coarse so as not to affect flow of fluid, for example, to the pump. Generally, the fluid filter by the U.S. Pat. No. 6,908,545 includes a high pressure filter module assembly comprising a high pressure manifold, a disposable primary filter element, and a high pressure filter bowl which is liquid-tightly connected at one end to the high pressure manifold and is closed at the other end. The high pressure manifold also includes a fluid inlet passage, a fluid outlet passage, a priority valve, a disposable secondary filter element, and a high pressure relief valve. Under normal flow operating conditions, the flow enters the high pressure manifold through the fluid inlet passage. The priority valve allows the flow to enter the primary circuit (flow through the primary filter element), and flow out through the fluid outlet passage. During peak flow conditions, the priority valve directs flow to the secondary circuit (flow through the secondary filter) and out through the fluid outlet passage. The high pressure filter module assembly utilizes the priority valve installed in the high pressure manifold to allow for continuous filtration of the hydraulic fluid up to a predetermined flow and pressure rates. The purpose of the priority valve is to guarantee that all available flow up to a predetermined flow rate will go to a primary (priority) circuit, including the primary filter element. Any excess flow rate will be diverted to a parallel secondary circuit. This parallel secondary flow or excess flow is filtered through a second filter element before the fluid exits through the outlet. The return filter module assembly also utilizes a priority valve installed into a return manifold that allows for continuous filtration of the hydraulic fluid up to a predetermined low flow rate.
The described hereinabove apparatus is also complex, expensive and inefficient.
Some well-known filter assemblies are generally of the tubular configuration having a removable end wall providing easy access to the interior of the filter housing for replacement of the filter elements, wherein one end of the filter element is supported on a central structural support, which also supports a bypass valve therewith. Such typical structure is depicted in U.S. Pat. No. 3,618,776 and it is apparent in such arrangement that there is little tolerance for variations in axial dimensions and that the central part of the filter element is obstructed to a degree by the central mounting posts. Further, a machined head is used as the closure member, this being a relatively heavy and expensive structure which is machined to fit the housing and which is tapped for receipt of the central support post.
Slightly different mounting of the filter element in a filter housing is described in U.S. Pat. No. 3,640,390 wherein a spider assembly is employed at one end of a filter element which together with a central compression spring at the other end serves to support the element within the filter housing. The entire filter housing is supported on and positioned relative to a threaded central fluid port. The position of the filter element with respect to the housing is substantially fixed and is dependent upon support provided at the inside diameter of the filter element. The support structure in this instance also houses a bypass valve therein and is removed with the filter element for replacement purposes.
The filter assembly with removable end structure by the U.S. Pat. No. 4,142,973, demonstrates a bypass valve of a particular configuration. In this apparatus the bypass valve is radially oriented in a head casting of the filter assembly at a position in line with the inlet port. The filter assembly works only for unidirectional fluid flow.
Another hydraulic fluid filter and bypass valve by U.S. Pat. No. 4,279,746 describes the apparatus comprising a tubular filter assembly having a mount for the filter element which positions the element both axially and radially and allows axial replacement thereof through a removable end wall of the filter housing. The inward end of the filter element is slidably supported on a fixed end wall boss. A bypass valve is retained in the mount in a compact arrangement with a portion of the valve within the filter element and removable therewith. More specifically in the detail, the apparatus includes
The device provides the forward and reverse fluid flows. The assembly includes a bypass valve therein which is inserted by a simple push-in and twist, snap-fit arrangement, and is similarly readily removable. The valve is insertable in a mounting aperture in either a forward or reverse direction and includes reversible components so as to be responsive to forward or reverse flow conditions. A “spider type” mounting member supports the filter element at the outside diameter at one end thereof, and positions same radially within the filter housing at a predetermined axial distance from the removable end wall. The spring at the other end of the housing bias the filter element and mount into engagement with the end wall so that the mount is positioned relative to the housing and to a radially oriented access port. A spacer on the mount provides a relatively unobstructed peripheral area for fluid flow at the outside of the filter element and assures a three-point mounting support in engagement with the inner wall of the filter housing for coaxial positioning of the filter element at the location of the outlet port. The “snap-in type” bypass valve assembly provides a reversible structure, wherein the central support pin, and spring may be reversed as well as the bypass valve mount containing the valve seat thereon for either forward or reverse flow operation at the same mounting location. Specifically but generally, the apparatus comprises a tubular metal housing, having a first end at which an end cover is removably attached, and a remote end, which includes a closure member consisting of a generally conical “shell-shape” member terminating in a tubular boss portion, the closure member, being secured to the tubular housing. The end wall of the closure member is open forming an inlet port to the housing. An outlet port, consisting of a radially disposed tubular member, is rigidly connected to the first end of the housing, thereby providing communication with the interior by way of aperture in the housing. A tubular filter element is secured at either end by a metal cap, having an annular elastomeric seal, which extends radially over the end and a short distance axially within that tubular filter element. The filter element is supported at one end on boss of the closure member, being biased to the left by compression spring surrounding the boss. A first spacer projects radially from the periphery of the seat at one end of the support. The second spacer, forming a part of the filter element mount, consists of the equally spaced axially extending projections of the side wall of the support.
Such known devices are extremely complex, require the presence of the springs, specific spacers, etc., and very expensive.
Those skilled in the art will readily observe that numerous modifications and advantages of the improved methods and apparatus for filtration may be made while retaining the teachings of the invention.
The implementation of the improved methods and apparatus for filtration provides the inexpensive and efficient method and device for law viscosity fluid filtration.
Thus, the known prior art does not provide the efficient, non-expensive and convenient methods and apparatus for filtration, and the present invention substantially departs from the apparatus/devices of the prior art.
It is understood, that these illustrations and drawings are the examples of the improved method and apparatus configurations and architectures, and those skilled in the art will readily observe that numerous steps, structures, modifications and advantages of the improved method and apparatus (i.e., methods and apparatus for filtration) may be made while retaining the teachings of the present invention.